paddlefish, large freshwater fish, Polyodon spathula, of the Mississippi valley, also called spoonbill or duckbill and named for its flattened, paddle-shaped snout. The largest specimens weigh well over 150 lb (67.5 kg) and reach 6 ft (183 cm) in length. The snout may be a third of the length of the body; it is equipped with sense organs that assist the fish in finding its prey of small crustaceans, which it strains out with gill rakers (see gill). Paddlefishes are primitive; unlike most modern fishes, they have skins with reduced scales, almost wholly cartilaginous skeletons, and upturned tail fins. They are uniform leaden gray in color. Valued as food fish, their greenish black eggs, like the more highly valued ones of the distantly related sturgeon, are used to make caviar. A Chinese species found in the Chang (Yangtze) River is said to grow to 20 ft (610 cm). Paddlefishes are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Acipenseriformes, family Polyodontidae.

Either of two species (family Polyodontidae) of archaic freshwater fishes with a paddlelike snout, wide mouth, smooth skin, and cartilaginous skeleton. It feeds with mouth gaping open, gill rakers straining plankton from the water. The American paddlefish, or spoonbill (Polyodon spathula), is greenish or gray and averages 40 lbs (18 kg); it lives in the open waters of the Mississippi basin. The other known species (Psephurus gladius), a larger fish with a more slender snout, inhabits the Chang (Yangtze) River basin. The flesh of both species resembles catfish; the roe can be made into caviar.

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